The present invention relates to a test technique to simulate the plane electromagnetic (EM) wave illumination of a conducting body. Such techniques are used in the testing of military vehicles such as aircraft for resistance to the effects of high intensity wide-band electromagnetic radiation. In the past such testing has been carried out simply by using antennae and appropriate generating equipment. In order to generate high intensity fields around a body as large as an aircraft such systems have necessarily been physically large and have had very high power consumption levels. In addition to being expensive to build and run such systems suffer the further disadvantage that they create high levels of radio frequency interference.
Illumination of conducting bodies at radio frequencies extending up to substantially 30 MHz is particularly difficult because of the large size of efficient radiation structures for these frequencies and the difficulty of focusing the radiated power on the body to be illuminated. Moreover it is found that at frequencies where the wavelength is 10's or 100's of metres that inductive coupling between the antenna and the aircraft occurs thereby distorting the electromagnetic field creating fields with spherical wavefronts and non-uniform field strengths. This distortion of the field severly restricts the diagnostic value of the test procedure.